A lot of multinuclear metal complexes having multiple metal nuclei in each molecule have been developed as highly active catalysts. Of these catalysts, a catalyst comprising a trifluoroacetate-bridged tetranuclear zinc cluster complex containing four zinc ions in a molecule is an excellent catalyst which promotes various reactions such as transesterification reaction, hydroxy group-selective acylation reaction in the presence of an amino group, acetylation reaction, deacetylation reaction, and amidation reaction in an environmentally friendly manner with less by-products (for example, Japanese Patent Application Publication No. 2009-185033, Domestic Re-publication of PCT International Publication No. 2009-047905, Japanese Patent Application Publication No. 2011-079810, J. Org. Chem. 2008, 73, 5147, J. Am. Chem. Soc. 2008, 130, 2944, Synlett 2009, 10, 1659, and Chem, Eur, J. 2010, 16, 11567).
The tetranuclear zinc cluster catalyst Zn4(OCOCF3)6O is an excellent catalyst, but it cannot be said that the activity of the catalyst is sufficient. As described in ACS Catal, 2011, 1, 1178, some reports say that the activity is improved to some degree by adding a nitrogen-containing aromatic compound such as DMAP (4-dimethylaminopyridine) or NMI (N-methylimidazole) to improve the activity; however, there still remains a problem of the need for an excess of the additive relative to the catalyst. Moreover, since the tetranuclear zinc cluster catalyst gradually decomposes and loses its activity with the progress of the reaction, the catalyst is difficult to recover and reuse.